The present invention relates to electronic thermostats which utilize frequency comparison to determine temperature. More particularly, the present invention is a low cost calibration system for calibrating the variable frequency input of a frequency comparing thermostat.
The analog-to-digital convertors that are used to sense room temperature in current thermostat designs have calibration problems. Either they do not have dynamic calibration for correcting errors in the system due to changes in temperature and aging of the hardware; or for designs which do have dynamic calibration for self-calibration, the self-calibrating means is expensive and the additional components take up valuable printed wiring board space.
Electronic thermostats which utilize frequency comparison means in order to determine the current room temperature are commonly used. An example of one such system is illustrated in U.S. Pat. No. Re32,960, entitled "Electronic Thermostat", issued to Michael R. Levine, and is hereby incorporated by reference. The Levine et al. system illustrated in U.S. Pat. No. Re32,960 is sensitive to errors which would be introduced due to shifts in component performance due to aging and temperature changes. Systems which have been utilized to correct for such errors utilize additional components and thereby increase the cost and the space required on the printed wiring board for the circuit.